Cultivated cucumber (Cucumis sativus var. sativus L.) is an important vegetable crop worldwide. It belongs to the family Cucurbitaceae. It is thought to originate from South East Asia from wild ancestors with small, bitter fruits, such as Cucumis sativus var. hardwickii. 
The cultivated cucumber genome has seven pairs of chromosomes (n=7) and a haploid genome size of about 367 Mb (Megabases) with an estimated total of about 26,682 genes. The cucumber genome was the first vegetable genome to be sequenced (Huang et al. 2009, Nature Genetics, Volume 41, Number 12, p 1275-1283 and http://www.icugi.org/cgi-bin/gb2/gbrowse/cucumber_v2/).
Yield of cultivated cucumber has not increased much over the last decades. Shetty and Wehner 2002 (CropSci. 42: 2174-2183) screened the USDA cucumber germplasm collection for fruit quality and fruit yield under field conditions in North Carolina (USA) and suggest that high yielding cultigens identified in their study can be used to develop high yielding cultivars.
WO2009/082222 used on of the accessions identified by Shetty and Wehner in 2002 (supra), the Turkish Beit-Alpha landrace PI 169383 to identify QTLs for fruit weight of harvest stage cucumbers on linkage group 3 and/or 4 of PI 69383.
Yuan et al. 2008 (Euphytica 164: 473-491) genetically mapped specific fruit traits in a cross between a Northern Chinese Cucumber S94 and a NorthWest European Cucumber S06. Their linkage group 3 appears to correspond to the physical chromosome 2 and their linkage group 2 appears to correspond to the physical chromosome 6. They mapped a locus called fw2.1 (fruit weight) to the top of chromosome 6 (LG2) and they mapped a locus called fw3.1 (fruit weight) to the bottom of chromosome 2 (LG3). They mapped a locus called fl3.1 (fruit length) to the same location as locus fw3.1, mapped based on the difference in fruit length between S94 (30 cm long fruits) and S06 (15 cm long fruits). However, they did not map total (cumulative) fruit yield.
Fazio et al. 2003 (Theor Appl Genet 107: 864-874) genetically mapped a number of traits, including cumulative fruits per plants over three harvests and morphological traits such as little leaf (‘ll’). Their linkage group 1 appears to correspond to the physical chromosome 6. A locus called fpl1.2 was consistent in both environments and mapped to the little leaf locus. Little leaf is physically located in the region spanning 7 Mb and 8.5 Mb of the physical chromosome 6, i.e. it is at the top of chromosome 6.
Wei et al. 2014 (BMC Genomics 15: 1158, p 1-10) disclose mapping of immature and mature fruit length and immature fruit weight in a population derived from a cross between a Chinese cucumber inbred line (CC3) and NC76. NC76 was developed from a landrace of Cucumis sativus var. sativus from Afghanistan (PI246930). They found a QTL for immature fruit length on Linkage Group 6.
WO2016/059090 and WO2016/059092 both describe two yield enhancing QTLs, one on chromosome 2 in the region of 0.4 to 2.9 Mb of the chromosome and one on chromosome 6 in the region of 26 Mb to the end of the chromosome, introgressed from a single wild cucumber into cultivated cucumber of the pickling type. Seeds of the cultivated pickling type cucumber comprising both QTLs in heterozygous form were deposited under NCIMB42262. The donor used in WO2016/059090 and WO2016/059092 was a different donor than the donor used in the instant invention.
Still, there remains a need for identifying QTLs for enhancing total (cumulative) fruit yield in cucumber to be able to increase fruit yield of modern cucumber varieties, especially in long cucumber types suitable for glasshouse cultivation e.g. high wire cultivation or the traditional umbrella system of cultivation. Especially, introgression fragments comprising yield increasing QTLs which do not comprise introgression regions which decrease average fruit length are needed. Also introgression fragments which are suitable for increasing average fruit yield in cold growing conditions are desired.